In recent years there has been a strong development of various storm water control systems to address the issues of stormwater runoff quantity and quality. One development has been the use of sub-surface water collection and storage chamber systems designed to retain stormwater surface flows and in particular, allow for a much slower discharge of stormwater effluents into receiving waters. Many of these systems are designed so there is a primary receiving chamber and several secondary chambers that line up end to end under impervious surfaces such as paved parking lots.
Arch shaped underground water collection and storage chambers are highly preferable to other types of underground water management systems. Unlike some other types of underground water management devices, arch shaped water collection and storage chamber systems are better equipped to be located under paved areas. These systems receive surface water, typically from wet weather events through surface drains into one or more primary water collection and storage chamber. These primary chambers are usually connected to a series of secondary water collection and storage chambers by a straight transfer device between the side wall of the primary chamber and an end wall of a secondary chamber. Usually these connecting pipes are approximately halfway up the wall of the chambers and are designed to transfer water from the primary chamber when the amount of water from the surface drain is such that drainage from the primary chamber is slower than the intake of the volume of surface flow. The transfer devices act as an overflow bypass mechanism and the transferred water accumulates in the secondary systems until the surface drainage ceases. At that time the secondary chambers either drain into the soils below if they are pervious, or in the case of impervious soils, drain out of a secondary drainage pipe into a secondary drainage system. In some cases the drainage water might be held for other uses such as, for example, irrigation.
One of the problems with these systems is that by utilizing a straight pipe as a water transfer device the water from the primary chamber passes to the secondary chamber with all of the debris, sediments and other pollutants that were washed off of the surface by the wet weather flow. These secondary chambers then accumulate this debris, sediments, and other pollutants throughout the system making maintenance expensive and time consuming. In many cases these pollutants can result in the failure of the system due to clogging and sediment buildup requiring removal of the surface material such as a parking lot in order to replace them. There is a clear need for water transfer devices that can minimize the transfer of debris and sediments and other pollutants from the primary chamber to the secondary chamber thus allowing the primary system to retain the debris and sediments and drastically reducing maintenance cost and time of the system.